I've been attempting to get my A3 to talk over serial with an x86_64 Linux computer for about a month now, with no luck. I've tried both USB and native serial ports, both with the same issue, seen below:

Attempting activation..
ERROR parseDroneVersionInfo,line 249: Drone version was not obtained. Please restart the program or call getDroneVersion
Automatic activation successful.
Failed to obtain control.
Your RC mode switch is not in mode F. (Is the RC connected and paired?)
This program will exit now.

I have the latest firmware (1.7) and am using the latest SDK (3.2). Does anyone know the proper serial configuration/flow control for communicating with the A3? The baud rates match and everything is seemingly correct. HOWEVER, when I use a serial monitor to view communications from the A3, they do not seem to be formatted as stated in the Open Protocol manual.

For the USB serial adapter, though, each line is prepended with character 0xFF. According to the open protocol every command should be prepended by 0xAA, correct? Any ideas why this would be incorrect? I've attempted changing the parity of the serial interface but with no luck (nothing changes - perhaps I have no control over the behavior of the port in the SDK).